Legend for figure 2-15:
Muffle chamber door
Elevating platform top
Elevating platform cover in stored
Miscellaneous equipment drawer
b. Operation. Make certain that the elevating platform is securely locked in the raised position before starting
(1) Muffle furnace.
(a) Connect electric furnace to electric outlet of cabinet, and push toggle switch to ON position.
(b) Set percentage timer. The timer operates so that heat is on for a set percentage of 1 minute and off
the remaining time. For example, with the timer set at 20, the heat is on for 20 percent of 1 minute and off 80 percent. A
setting at 60 controls temperature at approximately 1800 degrees F (982 degrees C). For quick heat up, set timer at 100
to provide continuous heating, but make sure to turn back timer when pyrometer shows temperature reading at 1800
degrees F (982 degrees C). Excessive temperatures will cause heaters, refractories, etc., to burn out.
(a) Prepare sample by use of the grease working machine.
(b) Place sample cup in proper position on penetrometer base.
(c) Insert needle or cone, as required, into chuck and tighten ,securely. Set dial needle to zero, add
weights to test rod as required, and adjust penetrometer by means of the coarse and micrometer adjustments.
(d) For detailed descriptions on setting up and operating penetrometer, and for information on testing
procedures, refer to applicable petroleum testing references.
c. Maintenance. Do not attempt other than organization preventive maintenance on the muffle furnace or
penetrometer. Defective parts should be referred to maintenance level specified in the maintenance allocation chart.
(1) Muffle Furnace.. Clean steel tray and muffle interior, using a clean cloth and mild soap-and-water solution.
Check to make sure that all electrical connections are tight.